The invention relates to a drive unit for an electric motor car which drive unit comprises an electric motor attached to a transmission unit, a housing for the electric motor through which a cooling liquid flows, and a control housing.
In electric motor cars liquid cooling is advantageous in spite of the cost involved because such cooling makes for low vehicle weight thanks to light-weight motors with high energy density. Liquid cooling also facilitates incorporation of the electric motor in the interior of the vehicle.
From practical experience, e.g., in crane construction, it is a known technique to design electrical motors with housings through which a cooling liquid flows. The output range of such motors is usually high and they are controlled from a control cabin in which the very voluminous controls are also located.
Electric motor car motors are relatively small. Their control, however, is very complicated so that they will meet all the requirements of operation (e.g., output control, control of rotational speed and direction of rotation, regenerative braking, battery charging, switching gears if these are provided, etc.).
These control operations are accomplished today using space-saving solid state output rectifying devices and control processors. Because of the high energy density of the power electronics and the thermal sensitivity of the processors, it is a general practice to distribute the controls at different locations within the motor space and to install the power electronics at a location receiving a generous amount of cooling air. This requires long and vulnerable (due to possible oscillations) connection lines. Despite these measures, cooling remains unsatisfactory while accessibility for diagnosis and repair is poor.
DE-OS 39 41 474 teaches to place the rectifier zones of a generator built into a liquid-cooled receiving cavity of a combustion engine within that area or in an adjacent area. A rectifier operates well at the cooling water temperature of the combustion engine. This temperature of approximately 80.degree. C. is unacceptable, however, for a control processor which controls the motor of an electric motor car.
It is therefore the object of the instant invention to construct a drive unit for an electric motor vehicle having a control processor in a compact and nevertheless thermally stable manner.